The case has been stated quite fully, in order that there may be no dispute as to what is involved and what not involved in its determination.
No question arises here as to the power of a state, consistently with the Federal Constitution, to make it a criminal offense for an employer, in purely private work in which the public has no concern, to permit or to require his employees to perform daily labor in excess of a prescribed number of hours. One phase of that general question was considered in Holden v. Hardy, 169 U.S. 366, 42 L. ed. 780, 18 Sup. Ct. Rep. 383, in which it was held that the Constitution of the United States did not forbid a state from enacting a statute providing-as did the statute of Utah there involved-that in all underground mines or workings and in smelters and other institutions for the reduction or refining of ores or metals, the period of the employment of workmen should be eight hours per day, except in cases of emergency, when life or property is in imminent danger. In respect of that statute, this court said: 'The enactment does not profess to limit the hours of all workmen, but merely those who are employed in underground mines, or in the smelting, reduction, or refining of ores or metals. These employments, when too long pursued, the legislature has judged to be detrimental to the health of the employees, and so long as there are reasonable grounds for believing that this is so, is decision upon this subject cannot be reviewed by the Federal courts. While the general experience of mankind may justify us in believing that men may engage in ordinary employments more than eight hours per day without injury to their health, it does not follow that labor for the same length of time is innocuous when carried on beneath the surface of the earth, where the operative is deprived of fresh air and sunlight, and is frequently subjected to foul atmosphere and a very high temperature, or to the influence of noxious gases, generated by the processes of refining or smelting.'
As already stated, no such question is presented by the present record; for the work to which the complaint refers is that performed on behalf of a municipal corporation, not private work for private parties. Whether a similar statute applied to laborers or employees in purely private work would be constitutional is a question of very large import, which we have no occasion now to determine or even to consider.
Assuming that the statute has application only to labor or work performed by or on behalf of the state, or by or on behalf of a municipal corporation, the defendant contends that it is in conflict with the 14th Amendment. He insists that the Amendment guarantees to him the right to pursue any lawful calling, and to enter into all contracts that are proper, necessary, or essential to the prosecution of such calling; and that the statute of Kansas unreasonably interferes with the exercise of that right, thereby denying to him the equal protection of the laws. Allgeyer v. Louisiana, 165 U.S. 578, 41 L. ed. 832, 17 Sup. Ct. Rep. 427; Williams v. Fears, 179 U.S. 270, 45 L. ed. 186, 21 Sup. Ct. Rep. 128. In this connection, reference is made by counsel to the judgment of the supreme court of Kansas in Ashby's Case, 60 Kan. 101, 106, 55 Pac. 336, in which that court said: 'When the eight-hour law was passed, the legislature had under consideration the general subject of the length of a day's labor for those engaged on public works at manual labor, without special reference to the purpose or occasion of their employment. The leading idea clearly was to limit the hours of toil of laborers, workmen, mechanics, and other persons in like employments, to eight hours, without reduction of compensation for the day's services.'
'If a statute,' counsel ovserves, 'such as the one under consideration is justifiable, should it not apply to all persons and to all vocations whatsoever? Why should such a law be limited to contractors with the state and its municipalities? . . . Why should the law allow a contractor to agree with a laborer to shovel dirt for ten hours a day in performance of a private contract, and make exactly the same act under similar conditions a misdemeanor when done in the performance of a contract for the construction of a public improvement? Why is the liberty with reference to contracting restricted in the one case and not in the other?'